In magneto-optic recording systems, digital information is stored in a thin magnetic storage medium by locally magnetized regions or domains. The regions are magnetized to represent either ones or zeros. The information is written into the magnetic storage medium by raising the temperature of localized small regions of the magnetic medium to the Curie point temperature of the medium at the localized regions. This lowers the coercivity to a point which enables orientation of the magnetic domain by an external magnetic field. The size of the regions or domains determine the density of the digital information. The size of the localized region is usually limited by diffraction and is marginally improved by use of shorter wavelengths of light and higher numerical aperture lens.
Stored information is read by Kerr or Faraday rotation of a polarized light beam incident on the magnetic medium by the magnetic fields at the magnetized regions or domains. The shift in polarization is in the order of one degree. This shift is employed to detect ones and zeros. Systems for reading out these small rotational changes are well established in the optical storage industry. Optical recording and the design of conventional read/write heads is described in the book entitled "Optical Recording" authored by Alan B. Marchant, Addison-Wesley Publishing, 1990.
In co-pending application Ser. No. 08/696,168 filed Aug. 13, 1996, incorporated herein in its entirety by reference, there is described a magneto-optic recording system employing near-field optics which includes a read/write head having a pair of crossed tapered optical waveguides terminating in slits supported closely adjacent to the recording medium to provide light coupling between the slit ends of the waveguides and the recording medium. The tapered waveguides are formed by etching a silicon wafer and filling the etched space with a transparent material. In one embodiment the tapered waveguides are filled with a material having a high index of refraction. The length of the waveguides and slits is greater than one-half the wavelength of the light transmitted by the waveguides wherein all light entering the waveguide is transmitted to the slits at the tapered end. The width of the slits at the tapered ends is a fraction of a wavelength of the light.